At present, in the light of environmental problems, resource problems and similar, solar cells as a source of clean energy are attracting attention. Silicon system solar cells are known as one type of solar cell; as silicon system solar cells there are ones which use single crystals, polycrystals, amorphous silicon, or similar. However, in silicon system solar cells generally problems such as high manufacturing costs, and moreover inadequate supply of raw materials remain, and so widespread adoption has not been achieved.
Further, compound system solar cells such as Cu—In—Se system (also called CIS system) have been developed, and have excellent characteristics such as extremely high photoelectric conversion efficiencies; but compound system solar cells have problems such as manufacturing costs, environmental burdens and similar, hence again widespread adoption has not been achieved.
In contrast to these solar cells, dye-sensitized solar cells have been proposed by a group led by Grätzel of Switzerland and others, and are attracting attention as photoelectric conversion elements which are inexpensive and capable of obtaining high photoelectric conversion efficiencies.
In order to increase the area of a solar cell, it is sufficient to reduce the current which generates to the extent possible and raise the voltage so as to suppress declines in voltage occurring due to the resistance within the photoelectric conversion element or in outside circuits. To do so, application of a series-connected type module construction is effective. In dye-sensitized solar cells, so-called W-type and Z-type series-connected module constructions, named for the shapes of the current paths, have been proposed (see Patent Reference 1).
FIG. 12 and FIG. 13 are diagrams showing the constructions in cross-section of such photoelectric conversion elements of the prior art. As shown in FIG. 12 and FIG. 13 respectively, in what are called W-type and Z-type photoelectric conversion element modules, the working electrodes (window-side electrodes) 108 are formed from a base material 101, transparent conductive layer 102, and semiconductor layer 103; light is incident on the working electrodes. On the other hand, the counter electrodes 109 are formed from a base material 101, transparent conductive layer 102, and catalyst layer 104. And, each of the photoelectric conversion elements of the module is constructed with an electrolyte layer (electrolytic solution or electrolyte gel) 105 sandwiched between the working electrode 108 and the counter electrode 109.
And, a W-type photoelectric conversion element module 100A can receive light from the rear surface by arranging each of the photoelectric conversion elements 110a, 100b, 100c, . . . , divided by partition walls 106, such that the working electrode 108 and the counter electrode 109 alternate between adjacent photoelectric conversion elements, as shown in FIG. 12. Further, the photoelectric conversion element module 100A has a construction in which the working electrodes 108 and counter electrodes 109 of pairs of adjacent photoelectric conversion elements 110a, 110b (110b, 110c) are provided on the same substrate 101 and interconnected.
On the other hand, in a Z-type photoelectric conversion element module 100B, photoelectric conversion elements 110a, 100b, 100c, . . . divided by partition walls 106, are arranged such that working electrodes 108 are placed on one side of the photoelectric conversion element module 100B, and counter electrodes 109 are placed on the other side, as shown in FIG. 13. And, the working electrodes 108 and counter electrodes 109 of these adjacent photoelectric conversion elements 110a, 100b, 100c, . . . have a construction in which the working electrodes 108 and counter electrodes 109 are joined and electrically connected by connection members 107.
However, in a W-type photoelectric conversion element module 100A, a construction is employed in which adjacent photoelectric conversion elements are interconnected in alteration on the front and on the rear, and the construction is extremely simple, but because half the cells receive light from the rear-face side, improvement of the conversion efficiency is difficult.
On the other hand, in a Z-type photoelectric conversion element module 100B, a construction is employed in which all photoelectric conversion elements face in the same direction, but it is necessary to connect the opposing electrodes between adjacent photoelectric conversion elements (the working electrode of one cell and the counter electrode of an adjacent cell), and there is a tendency for the manufacture of photoelectric conversion element modules to become troublesome. Moreover, control of distances between electrodes must be made uniform for elements over large areas, and a high degree of machining precision is required.
In Patent Reference 2 below, such a Z-type photoelectric conversion element module is described. In a photoelectric conversion element module described in Patent Reference 2, working electrodes are provided on base material used in common by the photoelectric conversion elements, and counter electrodes are provided on base material used in common by the photoelectric conversion elements. And, the working electrodes and counter electrodes are opposed, and the base material on which working electrodes are provided is bonded together with the base material on which counter electrodes are provided with a prescribed interval spaced. At this time, working electrodes and counter electrodes of adjacent photoelectric conversion elements are electrically connected using a conductive paste, to obtain a photoelectric conversion element module in which photoelectric conversion elements are electrically connected together.